Several types of protective headwear exist. Welding helmets are one example of protective headwear and some conventional welding helmets include an outer protective shell and headgear for supporting the outer shell on a user's head. The outer shell at least partially surrounds a user's head to provide protection.
One common activity that most welders perform on a daily basis is nodding of their welding helmets in order to move the outer shell from an upward, inoperative position, to a downward, operative position. The nodding motion, which may be comprised of a quick snap of the neck, applies stress on a user's neck muscles that can lead to long term neck issues. Additionally, the user's neck muscles can also be strained when they absorb a force generated by the outer shell coming to a jarring stop at a bottom limiting position.
Most welders do not recognize the health risk this daily action causes as the potential injury often manifests after a long period of time. Moreover, neck discomfort is accepted as the norm in the welding profession due to the rigorous requirements associated therewith. Significant angular velocity is created between the outer shell and the headgear of the protective headwear when a user nods the protective headwear.
Some conventional welding helmets allow a user to statically increase/decrease a normal force to increase/reduce the angular velocity of the outer shell relative to the headgear. Such welding helmets increase/reduce the angular velocity at a location where the outer shell pivots relative to the headgear. This is achieved in such welding helmets using a threaded fastener and a corresponding nut or knob, which can be rotated relative to the threaded fastener in either direction resulting in movement of the nut along the threaded fastener in both directions. A wall of the outer shell of the protective headwear is positioned between the nut and the headgear, and movement of the nut toward the outer shell and headgear applies more force, friction or normal force to the outer shell wall to decrease the angular velocity capable between the outer shell and the headgear. Movement of the nut away from the outer shell wall and the headgear reduces the force, friction or normal force applied to the outer shell wall to increase the angular velocity capable between the outer shell and the headgear.
One issue with tightening the nut and increasing the normal force is that, while it does reduce the angular velocity, it also increases the required applied force to overcome static friction between the pivoting components. As a result, more strain is applied on neck muscles due to a more violent nodding motion to initiate pivoting of the outer shell downward relative to the headgear.
Conversely, if the nut is too loose, then the initial nodding becomes easier, but the outer shell quickly accelerates to come to a jarring stop as it slams down on a stop member at a bottom limiting position. At the bottom limiting position, the force of impact is transmitted mostly to a user's neck muscles.